Abstract:
A tide gauge was installed at Cape Roberts in November 1990 and has been in near continuous operation since. A 10 minute average of water depth was recorded each hour with hourly averages of wind speed and direction, air temperature and solar radiation. From 2000 the recording frequency was increased from every hour to every 10 minutes. From 2003 data is read every 10 seconds and an average value ... (from 60 readings) is calculated every 5 minutes and recorded. Barometric pressure was measured as well, starting in 2003, with six barometric pressure readings made between 2 and 3 minutes in the 5-minute interval and averaged and recorded with the tide value. Each year the rise and fall of the sea ice is observed over a 2 - 3 day period during a spring tide using GPS. These measurements are related to a tide gauge bench mark and the sea surface to enable the reliability of the tide gauge to be checked. The tide gauge data is archived by Land Information New Zealand. The operation of the tide gauge has encouraged USGS and Ohio State University workers to establish Cape Roberts as a primary datum for their GPS stress and deformation control network in South Victoria Land. In 2000 LINZ in partnership with USGS have established a continuously recording GPS station at Cape Roberts that will also require continued tidal records.

Each season a geodetic grade GPS receiver is set up on the sea ice near the tide gauge and another is set up on a permanent reference mark ashore. The GPS “observes” the rise and fall of the tide by measuring the changing height of the sea ice. A hole is drilled through the sea ice to enable the height of the reference point of the GPS receiver above the sea surface to be determined. The relationship of the height of the shore-based reference mark and the zero of the sea level sensor is known. These connections enable the height of the sea surface as determined by the sea level sensor to be compared to the height as determined by the GPS measurements.

Quality
The tide gauge data is archived by Land Information New Zealand. Data for Cape Roberts since 8 November 2007 is available from the LINZ web-site (http://apps.linz.govt.nz/ftp/sea_level_data/ROBT/). Data prior to then: contact Glen Rowe, or (preferably) by sending an enquiry to customersupport@linz.govt.nz